Cyanobacteria surge at Nové Mlýny reservoir triggers emergency response

An overgrowth of cyanobacteria in the Dyje River and the Nové Mlýny reservoir in South Moravia caused a sharp drop in dissolved oxygen, prompting authorities to act. The state water management agency Povodie Moravy implemented extraordinary measures, including aerating the water with pumps, installing floating barrier walls (norné steny) to capture biomass, and continuously monitoring oxygen levels.

Oxygen concentrations remained at safe levels (6‑7 mg/L under the reservoir and above 2.2 mg/L above the Bulhary dam), and no fish deaths were recorded. Officials plan further interventions such as additional barriers if conditions worsen. Experts warned that the current bloom is more serious than last year’s event that killed about 30 tonnes of fish, linking the problem to prolonged drought, high summer temperatures and climate change. "Miroslav Láníček said this year’s situation appears even more serious than last year’s," and Povodie Moravy stressed ongoing vigilance.